1. Field of the Invention
The present invention relates to systems and methods for analyzing breath samples, and, more particularly, to such systems and methods for analyzing samples of breath condensate.
2. Description of Related Art
It is known in the art to analyze exhaled breath samples, for example, as a means to determine blood alcohol levels, and in anesthesia and critical care where inhalation anesthetic agents and exhaled carbon dioxide are routinely monitored. Infectious or metabolic diseases liberate specific odors that are characteristic of disease presence. Chromatographic techniques have identified volatile compounds in exhaled breath that can serve as potential markers for specific diseases. For example, Helicobacter pylori can be detected by a breath test for ammonia or radio-labeled carbon dioxide, and diabetic ketosis can produce acetone, which can be detected in the breath.
It is believed that exhaled breath sensing can provide noninvasive, point-of-care solutions to many medical applications, including illicit drug detection and medical condition diagnosis. In theory, any volatile compound in the blood stream can be found in the breath. Diagnostic breath test methods are known, but are expensive and time consuming, and must be performed in a laboratory by a trained technician.
Breath condensate analysis is a special case of breath analysis in which exhaled gas samples are cooled to a point at which the humidity in such samples condenses into a liquid, which is in turn collected. It is assumed that volatile markers, as well as biomolecules traveling as aerosols, partition into the condensate as well, and can be detected upon analysis of the condensate. It is known that a large variety of biomarkers can be found, including hydrogen peroxide, ammonia, and various peptides. As with normal breath gas analysis, such analytical methods are time consuming and require a trained technician and laboratory.
Condensate collection typically requires 10-15 minutes of breathing in order to obtain a 1-2 mL sample. This sample is then collected by syringe and transported to an analysis device (e.g., gas chromatograph/mass spectrometer, GC-MS). For example, Jaeger (a subsidiary of VIASYS Healthcare) produces a breath condensate collector called the ECoScreen, which uses gravity to collect condensate at the bottom of a macro-scale cooling tube. It is reproducible and prevents contamination by saliva, but, as mentioned above, requires 10-15 minute breathing times, as well as manual sample removal/transport. This causes discomfort for the patient, and requires a trained technician to handle and process the breath condensate samples.
Known existing exhaled breath condensate (EBC) collectors remain cumbersome and expensive, and utilize an external cooling system (often very bulky and power hungry) to condense out the breath. After collection of breath condensate the sample must be manually extracted and injected into sampling vials for appropriate analysis, thus exposing the sample to potential contamination and handling errors. The lack of a standardized method for how breath condensate is collected and handled makes it rather complicated for researchers to readily compare results and draw conclusions.
Recently, the American Thoracic Society (ATS) and European Respiratory Society (ETS) have jointly released guidelines for the collection and measurement of EBC biomarkers. The steps recommended by the task force are comprehensive and an excellent start for standardization of EBC collection. However, the main emphasis of the guidelines is to instruct researchers on the different variables that should be reported in literature, and comparing results and drawing conclusions from data measured with different environmental conditions still remains a challenge that has not been addressed.
Having an EBC collection device that is inexpensive, portable, and self-contained on the market would offer users an incentive to purchase and avoid custom development. It is difficult to make progress in EBC analysis if the condensate concentrations differ in back-to-back assays by as much as 50% due to poor collection techniques. Furthermore, a majority of known EBC devices collect the entire exhaled breath to maximize the total volume of condensate. It is well known that individuals have varying degrees of respiratory dead space and collecting the entire breath causes significant variability in measured results. Having a standardized collection system would help minimize variability between assays.
To date, there does not appear to be a strong push to utilize microfluidics for breath condensate analysis, which may be owing to lack of a direct interface between the macro sampling tools to the micro analytical procedures. None of the known EBC collection units addresses a means for efficient handling and transfer of condensate to an analytical system, leaving researchers to extract and prepare samples manually. Additionally, since analysis is done with macro-scale spectroscopy instruments such as gas and liquid chromatography, large sample volumes are required. Collection of EBC requires controlled breathing and as such it is desirable to collect for a short duration of time. Prolonged collection times can result in subjects hyperventilating and introducing uncertainties in collected sample. By utilizing microfluid-based sensors that could potentially be directly integrated into the EBC collection device, the need to sample for a long time can be removed and allow collection of samples with finer time resolution.
Therefore, it would be desirable to provide a system and method that can decrease the requisite collection time, thus alleviating patient involvement, and can automate the collection and analysis of breath condensate, such that reliable, point-of-care diagnostic information could be obtained. It would be especially desirable to provide such a system and method that can be used in the absence of an external cooling system.